It is well known that both mouse and human sperm carry numerous messenger RNAs and small non-coding RNAs into eggs during fertilization. Are these paternal RNAs essential for fertilization and early embryonic development? If so, what do these sperm-borne RNA molecules do once inside the cytoplasm of the egg? Theses fundamental questions remain unanswered because these RNA molecules are hidden deeply inside the highly compacted sperm chromatin. Thus, these sperm- borne RNA species are almost totally inaccessible without disrupting paternal DNA. We have generated two conditional knockout mouse lines, which produce sperm lacking miRNAs and/or endo-siRNAs. We will use these small non-coding RNA- deficient sperm to perform intracytoplasmic sperm injection (ICSI) to observe the fertilization rate and early embryonic development (Aim2). The RNA contents in these small RNA-deficient sperm will also be defined in comparison to those in normal wild-type sperm (Aim1). A negative finding would suggest that at least these two sperm-borne small non-coding RNA species are dispensable for fertilization and/or early embryonic development. However, if these two small RNA species are found to be essential for fertilization and/or embryonic development, then a more thorough study is warranted because the paternal contribution to fertilization or even early embryonic development has been hypothesized for a long time and it represents one of the most fundamental questions about factors that are required for the beginning of a life. Therefore, this exploratory study fits the high risk, high reward philosophy of the R2 funding mechanism. PUBLIC HEALTH RELEVANCE: The study will test whether two of the sperm-;borne small RNA species are required for fertilization and early embryonic development. Data from this study will potentially lead to discoveries of novel factors that are responsble for infertility, spontaneous abortion and birth defects.